Single plane scanning antenna



Sept 28, 1965 A. R. MACE ETAL 3,209,359

SINGLE PLANE SCANNING ANTENNA Filed May 27, 1963 JACOB TELLIER BY ALAN R. MACE @Ow-2. S. 477- 'yf'.

United States .Patent O 3,209,359 SINGLE PLANE SCANNINGANTENNA AlandR. Mace, lMillersville, Md., and Jacob Tellier, Mil- Waukee, Wis., assignors, by mesne assignments, to 4the United States of America as represented by the Secretary of the Navy Filed May 27, 1963, Ser. No. 283,645 .5 Claims. (Cl. 343-761) The presentrinvention relates to improvements in scanning antennas and more particularly to scanning antenna structures having alixedradiator.

Heretofore, scanning antennas'of theprior art generally utilize a reflecting element and a small radiator, both of whichare rotatedorlreciprocated in anarc as a unit. This type of antenna has many desirable characteristics but has an objectional mass in those applications wherein the antenna must scan through a` selected arc with great rapidity. In such applications, the windage and inertia of the reflector result in the necessity for very heavy mechanisms to drive the device and, in addition, demands considerable driving energy.

One method of eliminating a moving antenna reflector and its feed assembly has been to employ an optical system that provides the necessary scanning function. A spherical reflector and a refractive lens are provided, and scanning is accomplished by moving the microwave source along a circular arc which is concentric with the radius of the spherical reflector. This method, however, imposes severe requirements on the mechanical design of the scanner, and also the conventional system suffers from aperture blocking because of the interference of the feed structure and its drive mechanism with the reflected microwave beam.

In some radar applications it is desirable to scan sawtooth fashion, i.e., start the beam at one extremity of its scan, move it continuously at constant angular velocity to the other extreme, then return it directly to the starting position. The time required to return to an original position after reaching an end position is generally referred to as switching time and might be of an order of about two milliseconds. Experiments have shown that unreasonably large forces are necessary in order to achieve rapid switching times and consequently cam operated shutters, vanes, and oscillatory mechanisms in general, are not satisfactory.

In the present invention, rapid scanning in one plane is achieved by providing a stationary waveguide radiator and s. pair of rotating disks that direct energy from the radiator. By providing a discontinuous periphery on the disks, the beam can be scanned in one direction and a very rapid switching time can be obtained.

It is therefore a general object of the present invention to provide an improved scanning antenna having a fixed radiator.

Another object of the present invention is to provide an antenna that will search in sawtooth fashion.

Still another object of the present invention is to provide a scanning antenna that will have very fast switching action.

Other objects and advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing wherein:

FIGURE l is a top view, partly in section, showing one embodiment of the present invention;

FIGURE 2 is a diagrammatic view showing a scanning pattern of the embodiment shown in FIGURE 1 of the drawing;

3,209,359 Patented Sept. 28, 1965 ICC `FIGURE 3 is a top view of a discontinuous disk;

FIGURE 4 is a front view of the disk shown in FIG- URE 3 of the drawing;

FIGURE 5 is a side view of the disk shown in FIG- URE 3 of the drawing; and

FIGURE 6 is a diagrammatic view showing a sawtooth scanning pattern.

Referring now to FIGURE l of the` drawing, `there is shown a waveguide radiator 11 that is stationarily supported by antenna frame 12 and provided RF energy by a transmitter 13. A pair of disks 14 and 15 are positioned adjacent each side of radiator 11 and are rotatably mounted in antenna frame 12 by means of bearings 16 and 17, respectively. Disks 14 and15 are each provided with a reverse-bended ange that tapers gradually to the left for half its circumference and then reverses and tapers gradually to the right for the other half of its circumference.

Gears 18 and 19 are attached to disks 14 and 15, respectively, withv gear 18 being driven by motor means 21 through gear 22 and gear 19 being driven by motor means 21 through gear 23. Gears 22 and 23 are attached to shaft 24 that is rotatably supported in frame 12 by means of bearings 25 and 26, and as the gear ratio between gears 18 and 22 is equal to the gear ratio between gears 17 and 23, it can be seen that rotation of shaft 24 will cause disks 14 and 15 to be synchronously rotated.

In operation, transmitter 13 which is coupled to waveguide radiator 11 provides RF energy which is radiated in a straight direction as radiator 11 is stationarily mounted to frame 12. However, when motor means 21 is energized disks 14 and 15 are rotated and direct or reflect the radiated energy in a scan pattern. FIGURE 2 of the drawing illustrates the beam displacement when disks 14 and 1S are being rotated. FIGURE 2 shows that the beam starts at a zero (0) position, which is straight ahead, and then travels to a full right position at which position the flanges `on disks 14 and 15 are reverse-blended and the beam is then moved from a full right position to a full left position. At the full left position, the anges on disks 14 and 15 are again reverse-bended and the beam travels from left to the center position. One full cycle has been completed which describes a sine wave, and for each revolution of disks 14 and 15 the cycle is repeated.

FIGURES 3, 4 and 5 show a disk 31 that is discontinuous, that is, it has a break or a cut 32 through its flange. When a pair of disks 31 are mounted in a configuration such as that shown in FIGURE l of the drawing, the RF energy radiating from radiator 11 is scanned in sawtooth fashion as illustrated in FIGURE 6 of the drawing. As shown in FIGURE 6, when the beam has reached a full right position further rotation of disks 31 will cause the beam to go to a full left position without having the beam travel through a center, or zero, position. The slight delay between a full right beam position and a full left beam position is referred to as switching time, and by way of example might be of the order of two milliseconds when the scan cycle is of the order of twenty milliseconds.

It can thus be seen that the present invention provides an improved device that will provide rapid scanning of a radar beam. Also that a radar beam `can be scanned in sawtooth fashion with very fast switching action.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A scanning antenna device comprising,

a waveguide radiator,

first and second reflector disks rotatably mounted one each adjacent the sides of said waveguide radiator, each said reflector disk having a reverse-bended flange around the periphery thereof, and

means for synchronously rotating said rst and second reflector disks whereby energy from said waveguide radiator is directed by said disks as a scanning beam.

2. A scanning antenna system as set forth in claim 1 wherein said reverse-bended flange around the periphery of each said reflector disk is discontinuous whereby energy from said waveguide radiator is scanned unidirectional.

3. A scanning antenna device comprising, an antenna housing, a waveguide radiator stationarily attached to said houslng first and second reflector disks rotatably supported by said housing one each adjacent the sides of said waveguide radiator,

a gear train rotatably supported by said housing for synchronously driving said first and second reflector disks, and

means for driving said gear train whereby energy from said waveguide radiator is directed by said disks as a scanning beam.

4. A scanning device as set forth in claim 3 wherein each said reflector disk has a reverse-bended flange around the periphery thereof.

5. A scanning device as set forth in claim 4 wherein said reverse-bended flange around the periphery of each said reflector disk is discontinuous whereby energy from said waveguide radiator is scanned unidirectional.

References Cited by the Examiner FOREIGN PATENTS 607,294 11/ 47 Great Britain.

HERMAN KARL SAALBACH, Primary Examiner. 

1. A SCANNING ANTENNA DEVICE COMPRISING, A WAVEGUIDE RADIATOR, FIRST AND SECOND REFLECTOR DISKS ROTATABLY MOUNTED ONE EACH ADJACENT THE SIDES OF SAID WAVEGUIDE RADIATOR, EACH SAID REFLECTOR DISK HAVING A REVERSE-BENDED FLANGE AROUND THE PERIPHERY THEREOF, AND MEANS FOR SYNCHRONOUSLY ROTATING SAID FIRST AND SECOND REFLECTOR DISKS WHEREBY ENERGY FROM SAID WAVEGUIDE RADIATOR IS DIRECTED BY SAID DISKS AS A SCANNING BEAM. 